The invention relates to a laser arrangement for a multi-beam laser sighting mechanism, which comprises a light source for producing at least one primary laser beam bundle and an optical beam divider with reflecting surfaces for splitting at least one primary laser beam bundle into at least two partial beam bundles.
In the building industry, the long-known mechanical devices, which make alignment and measurement of the positional accuracy of building components, assemblies, installations and the like possible, are increasingly being replaced by optical devices, which are based on a high intensity collimated bundle of light rays. Since the semiconductor makes large numbers of laser diodes available with radiation in the visible spectrum, usually in the red region of the spectrum, a series of measuring devices has become known in the building industry, which replace the previously dominating mechanical, visual devices and methods and, moreover, also additionally offer new measurement possibilities. For example, sighting mechanisms, which send out at least one collimated laser beam bundle, which has a diameter of not more than 10 mm at a distance of 20 m and a deviation of about 1 mm/10 m in the horizontal direction have gained much acceptance. The laser beam bundle is usually aligned automatically in the horizontal direction by gravity-affected constructions or control circuits.
Aside from the horizontal alignment and leveling, there is frequently also the need to provide a plumb bob or to mark off a precise right angle. For this purpose, for example, U.S. Pat. No. 5,144,482 discloses a laser device, which emits three laser beam bundles, which lie in a horizontal plane and extend at right angles to one another. Additionally, the device emits two plumb bob beams. An arrangement of mirrors is provided within the device to produce the horizontal and perpendicular laser beam bundles. This arrangement of mirrors deflects the primary-laser beam bundle, originating from a laser diode, in the desired directions. The deflecting mirrors, for producing the total of five horizontal and vertical beam bundles, are disposed at a spatial distance from one another in the beam path of the primary laser beam bundle.
Consequently, a zero offset results for the three-dimensional coordinate system, put up by the emitting laser beam bundles, because the perpendicular beam bundles and the horizontal beam bundles have different virtual origins. Until now, the manufacturers of such laser beam devices, made do by providing a round gauge of, for example, 20 mm for this zero offset. For measurements with such laser devices, the zero offset must always be taken into consideration. In use, this represents a considerable source of errors. Due to the splitting of the primary laser beam bundle, coming from the light source, the intensity, remaining for the individual partial beam bundles, is greatly reduced. Admittedly, an attempt is made to provide a remedy for this disadvantage by using a laser light source of appropriately high output. This solution is hardly economically feasible, since the costs of laser diodes increase disproportionately to the power emitted. It is sometimes also desirable to produce partial beams in different colors. This, however, is not possible with conventional commercial equipment.
It is therefore an object of the present invention to provide economically feasible and practical solutions to these disadvantages of laser sighting mechanisms of prior art. The laser arrangement for a multi-beam laser sighting mechanism in accordance with the present invention indicates an optical system of coordinates, for which a zero offset is avoided. At the same time, this arrangement produces partial beam bundles having a sufficient intensity, so that even readings over larger distances are possible. This arrangement also produces partial beam bundles with different colors, without having to put up with losses in light intensity.
These objectives are accomplished by a laser arrangement for a multi-beam laser sighting mechanism, in accordance with the present invention. The inventive laser arrangement is constructed for use in a multi-beam laser sighting mechanism, which comprises a light source for producing at least one primary laser beam bundle and an optical beam divider with reflecting surfaces, by means of which the at least one primary laser beam bundle can be split into at least two partial beam bundles extending at right angles to one another. Pursuant to the invention, the light source comprises two semiconductor lasers, the light-emitting surfaces of which have a length extent and a transverse extent in a ratio of about 2.5:1 to about 4:1. The semiconductor lasers are disposed with their light-emitting surfaces such that the longitudinal dimensions of the light-emitting surfaces are rotated at an angle of 90xc2x0 to one another and the primary beam bundles, produced by the two semiconductor lasers, can be superimposed at a position before or at the beam divider.
A laser beam, emitted from a semiconductor laser, has an elliptical beam geometry, which is a consequence of the rectangular shape of the light-emitting surface of the layer of the semiconductor laser, producing the laser light. Due to the arrangement of the semiconductor laser that has been selected, with light-emitting surfaces rotated at an angle of 90xc2x0 to one another, the total laser beam bundle of the two superimposed elliptical primary beam bundles has essentially a star-shape, which results from the two ellipses rotated at an angle of 90xc2x0 to one another. As a result, the total beam bundle has an essentially symmetrical shape, which meets the geometric requirements of the beam divider. By superimposing the primary beam bundles of two semiconductor lasers, semiconductor lasers with low powers can also be used as a light source to produce a sufficiently high light intensity. Failure of one of the semiconductor lasers does not result in the total failure of the laser sighting mechanism; instead, it can still be used to a limited extent. As a result, the economic efficiency and the availability-of the laser sighting mechanism are further improved. Semiconductor lasers with different outputs and different wavelengths can also be used as light sources. As a result, interesting possibilities arise for varying the laser sighting mechanism with respect to the laser beams emitted. In the case of a three-dimensional laser sighting mechanism, for example, the at least three laser beams, setting up the Cartesian coordinate system, can have different colors. The user, therefore, can also get his bearings by relying on the-color of the projected marking.
To further improve the beam geometry and to improve the adaptation to the requirements of the beam divider, one or more beam-forming elements can be disposed at least between one of the semiconductor lasers and the beam divider.
In one embodiment of the laser arrangement, the light-emitting surfaces of the semiconductor lasers are disposed perpendicularly to one another. The two emitting primary beam bundles are directed onto a semitransparent mirror, which is disposed between the semiconductor lasers and the beam divider and inclined at an angle of 45xc2x0 to the direction of dispersion of the two primary beams and superimposed there into a total primary beam bundle. The selected arrangement is easily implemented and, aside from a semitransparent mirror, does not require any further optical elements of special construction. For the arrangement of the two semiconductor lasers selected, the beam divider has at least two and preferably four reflecting surfaces. The reflecting surfaces are at right angles to one another and disposed at the same distance from the semitransparent mirror. In each case, they are inclined at an angle of 45xc2x0 to the incident total primary beam bundle and protrude into the total beam bundle, such that a beam passage is formed for a portion of the total primary beam bundle. Due to the arrangement of the reflecting surfaces in the beam path of the primary light beam bundle, three partial beam bundles, extending perpendicularly to one another, can be easily produced. For example, the partial beam bundles, produced by the reflecting surfaces of the beam divider, form the orthogonal y and z axes. The portion of the total primary beam bundle, which is transmitted without hindrance, forms the x axis. For an arrangement of four reflecting surfaces, the total primary beam bundle is divided into a total of five partial beam bundles. In this way, xe2x80x9cnegativexe2x80x9d sections of the y and z axes can also be produced. The Cartesian coordinate system of partial beam bundles, so produced, has a common virtual origin, which arises from the intersection of the extension of the partial beam bundles through the xe2x80x9cpoints of incidencexe2x80x9d of the total primary beam bundle on the reflecting surfaces. The portion of the total primary beam bundle, transmitted without hindrance, also strikes this point of intersection. By these means, a zero offset is avoided. The arrangement of the reflecting surfaces provides the prerequisite for a compact and robust construction of the optical element. This facilitates the mounting in the laser device and reduces the susceptibility of the beam divider to jarring.
In an alternative embodiment of the laser device for a laser sighting mechanism, the light-emitting surfaces of the semiconductor laser are disposed at an acute angle to one another. The beam divider has at least two and preferably four reflecting surfaces, which are at the same distance from the assigned semiconductor laser. Pairs of these surfaces, each enclose an angle of 90xc2x0 with one another. The reflecting pair of surfaces is disposed at an angle of 45xc2x0 to the incident primary beam bundle. In this embodiment, the semitransparent mirror is omitted. The light-emitting surfaces of the two semiconductor lasers are oriented towards the reflecting surfaces of the beam divider and, only at the beam divider, are superimposed to form a total beam bundle.
In a further alternative embodiment of the inventive laser arrangement, the light-emitting surfaces of the semiconductor lasers are aligned parallel to one another. The beam divider is formed by two prisms, which have longitudinal axes extending perpendicular to one another and are disposed with their two prism surfaces at an angle of 45xc2x0 to the respective, assigned primary beam bundle. That prism, one of two plane parallel side surfaces of which is disposed in the vicinity of one of the prism surfaces of the second prism, has optically polished side surfaces. In this embodiment, the beam divider consists of two simple prisms, the reflecting prism surfaces of which enclose an angle of 90xc2x0 at the prism edge facing the semiconductor laser. The prism, through which a deflected partial beam bundle must pass without being refracted, has optically polished, parallel side surfaces and a passage, extending from the edge of the prism to the base surface, for a middle region of the incident primary beam bundle. The manufacture of the prisms is simple and economically cost-effective. They are mounted and aligned relatively easily in the laser equipment. The prisms are robust and largely insensitive to shock.
For manufacturing reasons and to improve the robustness of the construction, the reflecting surfaces of the beam divider are combined with one another into a structural unit. For example, the two prisms can be assembled into a matched unit. In a particularly advantageous variation, the reflecting surfaces of the beam divider are constructed at a monolithic component. The component may, for example, have the configuration of a truncated pyramid, the surfaces of the pyramid extending at an angle of 90xc2x0 to one another and at an angle of, for example, 45xc2x0 to the perpendicular.